The present disclosure relates to wireless telephone systems. The first generation of wireless telephone technology used analog mobile phones in which analog information signals were transmitted. As technology has progressed, 2 G, 2.5 G and 3 G systems have developed to handle higher-speed digital packet data, using wireless standards developed by industry consortiums such as the 3rd Generation Partnership Project (3 GPP) and the 3rd Generation Partnership Project 2 (3 GPP2). The next generation of wireless technology is referred to as 4 G technology, based on a standard known as long term evolution-system architecture evolution (LTE SAE) that uses orthogonal frequency division multiple access (OFDMA) technology. LTE networks consist of an evolved universal terrestrial radio access network (EUTRAN), an evolved packet core (EPC) network, and a packet network that hosts applications, which may be an IP multimedia subsystem (IMS) network.
In 3 GPP EPC networks, telephone handsets connect to packet gateways and establish bearers to access network resources, such as voice calls. Mechanisms exist in 3 GPP that allow preemption of existing bearers to allow access to new bearers. This mechanism, referred to as hard retention, allows a packet gateway to grant access to certain bearers even while in a resource-limited situation. However, allowing access to new bearers can cause existing bearers to get disconnected, leading to customers experiencing “dropped calls.”